There is a central debate in foreign relations law between scholars who argue that the President inherited great power from the founding and those who contend that only after World War II was there a significant shift in the balance of powers over foreign relations. This Article highlights a third perspective by focusing on the significance of presidential assertions of power during the decade after the Spanish-American War. In this period, presidents asserted unprecedented power to dispatch the armed forces of the United States into foreign conflicts and to independently enter into binding international agreements without the participation of Congress. The Article concludes that shifting international relations, shaped by strategic foreign policy doctrine, have been central drivers of presidential assertions of authority over foreign relations.